Under what condition can a pilot allow a person under the influence of intoxicants to board the aircraft?

A pilot can allow a person under the influence of intoxicants to board the aircraft if they are a medical patient under proper care. This is because there are specific circumstances in which individuals may be transported due to medical needs, and in such cases, the welfare of the patient is paramount. The requirement for proper care suggests that the individual's health is being managed by qualified personnel, which can mitigate the risks typically associated with flying while intoxicated.

The other scenarios presented do not meet the same criteria. For instance, allowing someone to board simply because they are accompanied by a sober adult does not ensure the safety of the flight or adherence to regulations. Similarly, educational purposes during training cannot justify boarding someone impaired, as safety remains the primary concern. In the event of a medical emergency, while it might seem reasonable to allow an intoxicated person onboard, the circumstances would need to be well-defined and managed to ensure safety for all involved.